Among the cereal flours, wheat flour has the ability to form a strong, cohesive dough that retains gas and produces a light, aerated baked product. Wheat proteins, and more specifically the gluten proteins, are believed to be primarily responsible for that uniqueness of wheat. When wheat flour is mixed with water, a cohesive, viscoelastic dough is formed. The viscous part is sometimes referred to as plastic viscosity or plasticity. No other cereal flour forms a dough with a similar viscoelastic character. Furthermore, it is generally established that the gluten proteins govern the bread-making quality of the various wheat flours. Flours milled from different wheat cultivars vary widely in their loaf volume potential. Even at constant protein content and using the same baking process, it has been shown that a large variation in loaf volume can still exist. Thus, the quality of the protein in wheat can vary. The quality characteristics of protein are often referred to as functional properties and gluten strength (R. Carl Hoseney, Principles of Cereal Science and Technology, 2nd Ed, 1994, by the American Association of Cereal Chemists Inc.) Therefore, the total amount of gluten protein in a flour, the protein quantity, is also important and also the protein quality thereof.
In fact, different types of wheats, in addition to their use for bread production, are the raw materials for an enormous diversity of products e.g a huge variety of pasta products, noodles, cakes, biscuits and wafers. Also, for these types of products both the protein or gluten quality and the protein quantity are important. For example durum wheats with stronger gluten quality generally give pasta with a stronger “al dente” and relatively strong gluten quality flours give cooked noodles a chewy and elastic texture. Preferences may vary between markets e.g. such that in Korea and China noodles with a chewy texture are preferred whereas in Japan a softer texture is desired.
It follows that there is a need in the wheat and wheat processing industries to provide a rapid, accurate and objective wheat quality assessment to ensure and preserve the optimal quality for a specific use and to establish a fair price for a specific consignment both in domestic and international trade.
So called rheological instruments such as the Mixograph (National Manufacturing, Lincoln, Nebr., USA), the Farinograph (Brabender GmbH, Duisburg, Germany) or the Alveograph (Chopin Technologies, Villeneuve-la-Garenne, Cedex, France) have long been used in the flour milling industry to monitor flour quality, especially in relation to breadmaking. (Tronsmo et al, Cereal Chem. 80(5):575-586). These instruments are empirical, introduced already in the 1930's and typically used on flour which means that when testing wheat, the wheat sample first needs to be milled to a flour.
Furthermore, the testing time in the equipment is long and instruments are also laborious in terms of cleaning between tests.
In practice this means that only a few tests per day can be carried out. Because of their empirical nature results are not expressed in fundamental scientific units but are manufacturer specific and expressed in e.g. Brabender units, which often are unique for the specific instrument used. This makes standardization of the instruments difficult and may lead to discrepancies between results from different users of the same type of equipment.
Fundamental rheological measurements were introduced on dough also as early as 1932 (Schofield and Scott Blair). Fundamental rheological instrumentation is designed to measure viscoelastic behavior in scientific units and also so that viscous and elastic components of the material under test can be separated. For example (Faubion and Hoseney, 1990) described dynamic oscillatory measurements applied to dough systems. Stress relaxation techniques applied to flour doughs were described by for example (Launey and Bure, 1974) and creep recovery techniques on flour doughs by for example (Bloksma and Bushuk 1988). Fundamental techniques have thus been well used in the research community but have not been adopted in the wheat industry. The main reasons are that fundamental rheological research equipment is very expensive, designed for a research lab environment, complex to use, requires technical personnel and the measurement times are very long. The instrumentation itself is not specifically designed and adapted for wheat quality measurements but of general design for a variety of materials.
For the purpose of grading and segregating wheat in order to provide a consistent quality of wheat for industrial processing and to determine a fair price to the supplier or trader of wheat, it is necessary to rapidly and with acceptable accuracy determine the quality of wheat. Specifically, there is a need to supply a consistent quality of wheat, or of products produced from wheat and to determine the quality of wheat because different end use purposes or market preferences demand different quality characteristics for optimal manufacturing performance or customer or consumer acceptance.
It follows that there is still a need in the wheat and wheat processing industries to provide a rapid, accurate and objective wheat quality assessment based on a fundamental technique that can be adopted in an industrial environment in a flour mill or at a wheat receival site and used by non technical personnel. Specifically, such rapid assessment will also help blending wheat or flour streams in an informed manner to a desired end product. It will help map production lines and precisely help controlling end use quality avoiding e.g. production waste and plant downtime, thereby corresponding to real functional and industrial needs.
The objective of the present invention is to fulfill these needs.